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« 







-HANDBOOK 

FOR 

Process Photographers 


A Practical Guide to the Making of 
Line and Half-Tone Negatives by 
the Wet Collodion Method 
For Use in the Photo- 
Engraving Process 



BY 

EVERETT R. EATON. 


Copyright 1921. 









Tn°0° 



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INTRODUCTION. 


The purpose of this book has been to 
provide a practical guide for the beginner or 
apprentice, who desires to make himself bet¬ 
ter acquainted with the details concerning the 
production of line or half-tone negatives by 
the wet-collodion process. 

The importance of the study of the sci¬ 
entific laws upon which the practical work 
is founded cannot be too strongly urged, as 
it is the possession of this knowledge which 
makes the difference between an intelligent 
operator and a “hit and miss” workman. The 
principles underlying the art are not so mys¬ 
terious or vague, but what anyone with a 
little study.and practice can arrive at a clear 
conception of their meaning.' The explana¬ 
tion relating to screen distances, stop open¬ 
ings, etc., has been dealt with in its logical 
order. The results sought after will not come 
haphazard, but must be gotten by careful 
workmanship, based on definite scientific prin¬ 
ciples. 

Whatever have been the errors of omis¬ 
sion or commission, the writer has conscien- 
sciously tried to present the various details 
of the work in such a manner that it will 
be of benefit to the largest number of stu¬ 
dents and beginners. 


LINE NEGATIVE MAKING 

BY THE 

WET COLLODION PROCESS 


THE COPY TO BE REPRODUCED 

The first consideration in the making of 
a line negative for the Photo-Engraving 
Process is the copy to be reproduced. It 
should be preferably a drawing or sketch in 
good black ink on perfectly smooth white 
paper or card. This is placed on the copy- 
board so as to lie absolutely flat. A piece 
of clear glass placed over the copy will ac¬ 
complish this and will also prevent any 
creases from showing. If the copy lies in 
rolls or is not parallel with the ground glass 
and sensitive plate, there will be a distor¬ 
tion in the resulting image. 

FOCUSING THE IMAGE 

Our next step is to focus the image on 
the ground glass sharply, reducing or en¬ 
larging it according to requirements. This 
is done by placing the ground glass focusing 
frame in position, opening the lens up wide 
to admit as much light as possible, and then 
with the aid of a focusing cloth to exclude 
all the light except that which passes through 
the lens, making the necessary adjustments. 
The operation will be found simple enough 
if we remember that the nearer the lens or 
camera as a whole is to a copy board, the 
larger will be the image, and the farther 
away, the smaller it will be. Sharpness is 
obtained by moving the ground glass back 
and forth until it is in the same plane at 
which the rays of light reflected from the 
copy come to a focus in back of the lens. 


— 4 _ 



MEANING OF “FOCAL LENGTH” 


This is definite, as every lens has a cer¬ 
tain focal length; that is, the rays of light 
when an object 100 feet or more is focused 
on, or in other words, when they are com¬ 
ing parallel, come to a point or focus at a 
certain distance from the nodal point or op¬ 
tical center of the lens. The distance will 
be found with most lenses to be about equal 
to the diagonal of the plate for which it was 
intended to cover. In the case of an 8x10 
plate, thirteen inches is about right. This, 
however, does not mean that smaller plates 
cannot be used with it. 

CENTERING THE IMAGE 

Great care must be taken to see that 
the image is centered on the ground glass, 
or else it may not be in the right portion on 
the sensitive plate. Moving the copy board 
to the right or left or up and down, or mov¬ 
ing the lens, changes the position of the copy 
on the ground glass. 

AVOIDING REFLECTIONS 

The last precaution to be taken before 
making a plate ready preparatory to expo¬ 
sure, is to see that there are no reflections 
from the copy, as this is quite likely, if the 
original has been covered with a piece of 
glass. Stand beside the camera and place 
the head in front of the lens, looking directly 
at the copy. If there are any reflections from 
windows, etc., they will quickly be noticed 
and can be screened out. 

We are now ready to prepare a plate for 
exposure in the camera. 

REMOVING OLD FILM 

Pieces of glass of the desired size (for 
practice work 5x7 will be found plenty large 
enough) are placed in a crock of lye solu¬ 
tion: 


Crude Caustic Soda,...2 lbs. 

Water . 1 gal. 


This will loosen the old film which may 
have adhered to the glass from previous use. 
Sometimes straw is placed in the receptacle 
alone 1 with the glass to separate it thus pre¬ 
venting it from sticking together. In any 
case, the glass should be placed in the solu¬ 
tion one at a time, so that both sides will 
be affected by the lye. After being allowed 
to stand for twenty-four hours, the glass is 
taken out and scrubbed thoroughly on both 
sides with a stiff bristle brush. 

FURTHER CLEANSING IN ACID 

It ; s then placed in another crock of di¬ 
lute nitric acid: 


Nitric acid .1 qt. 

Water . 1 gal. 


This further removes any organic mat¬ 
ter and renders them chemically clean. Af¬ 
ter standing another twenty-four hours, they 
are taken out and washed under the tap to 
remove all traces of the acid, and then while 
still wet, flowed with the following solution: 

White of one egg (= about 1 oz.) 

Ammonia (acts as preservative) 

. 15 drops. 

Water . 32 oz. 

ALBUMENIZING 

The egg must be well dissolved and the 
solution filtered. After flowing over once 
with the solution and draining (this removes 
the excess of water), it is flowed again, 
drained and placed in a rack to dry. The 
excess solution from the second flow may be 
drained back into the pouring glass and used 
again. A piece of cheese-cloth tied around 
the lip of the graduate will prevent bubbles 
from getting on the plate. For convenience 
sake, it is best to place the albumenized side 










always one way, as when the plates are dry 
it is very hard to detect which side has been 
coated, although sometimes it is possible to 
tell by rubbing the finger nail over both sur¬ 
faces—the smoothest is generally the coated 
side. If the plates were not coated with this 
substratum, it would be impossible to make 
such a substance as collodion adhere and not 
be rinsed off during the operations of wash¬ 
ing. 

SENSITIZING THE PLATE 
(Collodion.) 

We are now ready to sensitize a plate 
for exposure in the camera. It is first flowed 
with a solution of collodion. This in the plain 
form is a mixture of pyroxyline or gun-cot¬ 
ton dissolved in equal parts of sulphuric ether 
and grain alcohol. This alone, if kept well 
stoppered, will keep indefinitely. To it are 
added, however, such halogen salts as will 
be found necessary. These salts of chlorine, 
bromine and iodine, when dissolved in ether 
and alcohol, especially for this purpose, are 
called the “iodizer”. Many of the engraving 
firms at the present time prefer to buy a 
collodion base with the iodizer separate, and 
mix together as needed. This has the ad¬ 
vantage that a large amount need not be 
made up at a time, and thus any waste from 
spoiilinp* with age is avoided. For those who 
prefer to mix their own, the following for¬ 
mula will be found equally suitable for either 
line or half-tone work: 


Ether . 16 oz. 

Alcohol . 16 oz. 

Cadmium Iodide .75 grs. 

Ammonium Iodide .45 grs. 

Calcium Chloride .15 grs. 

Strontium Chloride .15 grs. 

Gun-cotton . 175 grs. 


The iodides and chlorides are dissolved in 
part of the ether and alcohol and then added 
to the remainder. The cotton is then added 











and allowed to thorougniy dissolve. me 
iodizer, as the prepared solution is called, 
will also keep indefinitely, but when added 
to the ether and alcohol, the whole solution 
after three or four weeks, gradually turns 
to a deep red, at which stage it will be found 
practically useless, This red color is caused 
from the iodine being liberated, and this 
iodine in such quantity acts as a great re¬ 
strainer, thereby making the plate less sen¬ 
sitive to light. The most desirable color is 
of a rich straw yellow. New or “green” col¬ 
lodion will be found to work very fast and 
have a tendency to give fuzzy or veiled images, 
while old or too “ripe” a collodion will work; 
iust the opposite. The effects which the va¬ 
rious iodides and chlorides have in the col¬ 
lodion are as follows: Cadmium iodide gives 
softness, ammonium iodide gives contrast, 
strontium chloride gives density and acts as 
a preservative, while calcium chloride absorbs 
the excess of moisture in the solvents. An 
excess of ether closes the pores in the film 
so that the silver salts do not penetrate as 
well, while an excess of alcohol makes the 
film porous and rotten. This is the reason 
why old collodion gives a rotten, crumbly 
film, as the ether evaporates more in pro¬ 
portion to the alcohol. In warm weather, 
because of rapid evaporation, and in flowing 
large plates, it is better to use more ether 
and alcohol for a given amount of solution. 
Always keep water out of the collodion, as 
water in the solution will precipitate the gun¬ 
cotton. If using a freshly iodized collodion 
for line work, be careful not to over-expose. 
The best results can be gotten with a col¬ 
lodion that has been iodized for some time 
and is well “ripened”. 

COATING WITH COLLODION 

Before coating a plate it should be care¬ 
fully dusted with a camel’s hair brush, kept 
especially for the purpose. Always brush 


— 8 — 


both sides and in one direction. A brisk back 
and forth movement will simply attract more 
dirt and dust to the plate. 

Hold the plate with the albumen side up 
in the left hand with the first two fingers 
underneath and along the edges, and the 
thumb on top on the. corner. The collodion, 
which, of course, has been carefully filtered, 
as any dust or dirt in the film leaves a mark, 
is flowed in a pool on the' upper part of the 
plate, the right top corner being covered 
during the pouring and the plate gently tilted 
so that the left corner is next covered, then 
the left bottom corner, and finally the ex¬ 
cess of collodion drained off at the right bot¬ 
tom corner, as shown in the illustration be¬ 
low. During these operations, the bulk of 
the collodion should be kept on the center 
of» the plate, which is only tilted enough for 
the collodion to flow to the edges, but not 
over it and off the plate. At all times care 
should be taken to see that the collodion is 
kept flowing forward and that no “flow-back” 



Right Way 


Wrong Way 


occurs, otherwise the collodion will thicken 
and cause a mark in the negative. The 
draining of the excess collodion should be 
done gradually, the plate being tilted slightly 
at first, and then gradually brought to a ver¬ 
tical position. During the whole time of 
draining the plate must be rocked back and 
forth to prevent ribbed marks from running 


— 9 — 


towards the draining corner. After the col¬ 
lodion has started to set, it is a good plan 
to scrape off the right and bottom or heavy 
edges, as they contain ether and alcohol, 
which is ruinous to a silver bath. When the 
film has set sufficiently, which is ascertained 
by touching the lower right hand corner and 
noting if the greasiness has disappeared, the 
plate is ready to be immersed ijn the silver 
sensitizing solution in the dark-room. 

SILVER BATH 

The silver bath or sensitizing solution is 
made by dissolving silver nitrate in distilled 
water until it tests between 40 and 45 de¬ 
grees by the hydrometer or argentometer. If 
ordinary tap water is used, the bath must 
be set in the sun until the organic matter 
present has settled to the bottom as a black 
precipitate and then filtered. Nitric acid is 
now added drop by drop until blue litmus 
paper turns red in a few seconds, or between 
12 and 18 drops for every 24 ounces of so¬ 
lution. Before use, the bath must be iodized. 
A plate coated with collodion left in for sev¬ 
eral hours will be sufficient, or if the bath 
is to be used at once, a few crystals of iodine 
will answer the same purpose. If the bath 
does not contain a certain amount of iodine 
to act as a restrainer, the action of the sil¬ 
ver nitrate in combining with the -iodides in 
the collodion will be so great as to cause 
minute pin-holes over the entire surface of 
the plate. 

The collodionized plate is now placed in 
the silver bath and allowed to stand for three 
or four minutes. If a tray is used instead 
of a glass dipping bath, it must be rocked 
occasionally during the time of immersion. 
In lowering the plate into the bath, care must 
be taken to do it with an even, steady mo¬ 
tion, for if this is not done, a streak will be 
the result. The plate must not be removed 
too soon, as it will not be sufficiently light 


-10_. 


sensitive and will be streaked, whereas, if 
left too long, it will look blue and thin on 
being taken out, and wtill give a weak image. 
A bath testing much less than 40 degrees 
necessitates leaving the plate in for an ab¬ 
normal length of time, and if over 45 de¬ 
grees, the plate will look streaked on being 
taken out and will have a veil or deposit over 
the entire surface. The chemical action in¬ 
volved when a collodionized. plate is placed 
in the silver bath is known as double decom¬ 
position. The ammonium 'iodides, for ex¬ 
ample, combine with the silver nitrate to form 
silver iodides (a light sensitive substance) 
and the ammonium nitrate is thrown off as 
a by-product. 

After the plate has been allowed to re¬ 
main in the bath for the desired length of 
time, it is raised carefully out of the con¬ 
tainer, drained, and the back wiped dry with 
a tuft of cotton. In holding the plate dur¬ 
ing this operation, it is necessary to keep it 
in such a position that any dirt from the 
hands will drain along the lower edges and 
not across the surface. 

On holding the plate to the dark-room 
light, it will be seen to have a rich lemon 
yellow, not blue or not too much of an orange. 
Too blue and thin generally means too much 
acid in the bath, while if too orange, then 
there is not enough. It is now placed in the 
plate holder with the emulsion side away from 
the operator. Strips of blotting paper about 
a half inch wide should be laid along the sil¬ 
ver clips at the bottom to prevent any dirt 
from them being drawn onto the surface of 
the plate by capillary attraction, and also to 
prevent the excess silver solution from drip¬ 
ping on other parts of the holder and rotting 
the wood, as the silver is very corrosive. 
Now close the door of the holder, fasten and 
be sure the slide is firmly in place. In car¬ 
rying the holder to and from the dark room 
and camera, it should always be held in an 


-11 


upright position and not tilted around or laid 
down flat, as the silver solution is apt to run 
back across the surface of the plate and cause 
markings. Now after bringing the holder out 
from the dark room, place it in the position 
that the ground glass occupied, remove the 
slide, and cover all with the focusing cloth 
to prevent any possibility of light leaking in 
and fogging the plate. The ark lamps placed 
one on each side of the camera should be ad¬ 
justed to illuminate the copy as evenly as 
possible, and reflectors used to concentrate 
the light and also to prevent it from shin¬ 
ing directly into the lens. 

EXPOSING 

Before removing the cap from the lens, 
the diaphragm should be turned down to 
about F32, or in the case of stops, one in 
size to correspond with that reading for that 
particular lens should be placed in the slot 
provided for that purpose. Often the ques¬ 
tion is asked, “Why do we use such a small 
portion of the light that might be allowed 
to pass through the lens? Surely, the more 
light, the less exposure." Simply this: All 
lenses, due to an inherent law of optics, are 
subject to various abberations, such as, 
spherical, chromatic, etc., and it is at their 
outer margins that they are the least cor¬ 
rected. Therefore, by using only the cen¬ 
ter or more fully corrected portions, we are 
able to secure sharper images and without 
distortion. Now in exposing, remember this: 
the greater the enlargement of the original 
copy, the more exposure necessary, and vice 
versa, or also, the greater the bellows ex¬ 
tension (distance from nodal point or optical 
center of lens to ground glass) the more the 
exposure, as this distance varies accordingly. 
The reason for this variation in exposure is 
plain. A certain volume of light governed 
by the size of the stop passes through the 
lens. Now if we spread it over a large area, 


- 12 — 


q 1 
P k i 

1* .5 

PROPORTINAL EXPOSURE TAQlE 
The following tablejjives the correct time 
for all different reductions and enlarge¬ 
ments when the same stop is used. 

78 

:5Z 

‘63 

■95 

126 

/■5?,2 

3W 

! /t 

33 

.65 

98 

/ 3 

/ 6 

326 

76 

35 

68 

/’ 

136 

57 

35 

Vs 

’36 

72 

/•/ 

m 

/'8 

3 6 

Vi- 

V 

8 

rz 

V6 

20 

3 9 

73 

55 

9 

I'd 

178 

222 

5H 

/ /z 

56 

/'/ 

17 

79 

28 

5625 

3/5 

76 

//53 

23 

306 

33 

7656 

7/8 

88 

176 

27 

3 5 


832 

S/Jce 

/ 

z. 

3 

V 


/o 

/'/8 

773 

2Z6 

3 5 

55 

56 

UZ9 

/'/i 

52.7 

253 

3 8 

506 

6 3 

/Z-66 

f/z 

/56 

3/2 

5-7 

63 

7-8 

15625 

2 

ZZ5 

T5 

675 

9 

/fZ5 

225 

3 

V 

Q 

!Z 

/6 

20 

50 

5 

6Z5 

/Z‘5 

/&75 

25 

3/25 

6 Z5 

5 

9 

/a 

Z7 

36 

¥5 

90 

6 

IZ-Z 

255 

363 

59 

6/25 

IZZ5 

7 

16 

32 

58 

65 

80 

160 

3 

2026 

505 

6075 

8/ 

jorzs 

ZOZ‘6 


-13- 

































as in the case of an enlargement, there will 
be a resulting thinner layer than if we con¬ 
centrate it over a small space. On the op¬ 
posite page will be seen a table with rela¬ 
tive exposure values for different amounts of 
enlargement or reduction. Aside from the 
size of stops and amount of enlargement or 
reduction, the strength of the lights and char¬ 
acter of the copy have to do with exposure. 
Tlie light reflected from a bluish white copy 
will affect the plate more than that reflected 
from a yellowish white copy, as wet collodion 
plates are affected most by the blue and blue- 
violet or actinic rays of light. 

DEVELOPING 

After the plate has been exposed for a 
sufficient length of time, the lens is capped, 
slide placed in position in the holder and 
plate holder removed to dark room. Upon 
removing plate from holder, no change will 
he noticeable—the image is in what is known 
as a latent state. The light has brought about 
a certain change in the silver iodides in the 
emulsion, but exactly what is a matter of 
speculation. However, it is supposed to be 
this: for every molecule of silver iodide 
wherever the light has acted, one atom of 
iodide has been liberated. These resulting 
sub-salts, as they are called when the iodine 
has been liberated, have one important prop¬ 
erty, namely: an affinity for reduced silver 
nitrate. Now to bring the image into a vis¬ 
ible state, it is only necessary to treat the 
plate with some substance which will reduce, 
the surface or free silver to the metallic form 
thereby allowm™ it to attach itself to the 
aforementioned sub-salts in relative position 
to correspond with wherever the light has act¬ 
ed. Actually this is exactly what is done. This 
solution or developer, as it is called, is made 
up of: 

Iron Sulphate (to test 25 degrees 
by hydrometer) .64 oz. 


- 14 - 



Acetic Acid No. 8 (28 per cent 

Commercial) .8 oz. 

In flowing- the solution over the plate 
care must be taken to cover the entire sur¬ 
face evenly and at as near the same time as 
possible. If this is not done, certain portions 
will be acted upon longer than others, and 
a streak will result. The plate should be 
held in the left hand much in the same man¬ 
ner as when flowing with collodion, and the 
developer flowed along the right and heavy 
edge. The developer should not be flowed on 
with a rush as wherever it strikes the plate 
very hard, the silver is washed away from 
that portion, and a thin spot will result. 
Proof of this theory in regard to the con¬ 
tention that density is built up from the sil¬ 
ver on the surface of the plate as it is re¬ 
duced by the developer, is found in the fact 
that, should the plate be washed thoroughly 
after exposure and before development, no 
image of any density can be gotten by any 
amount of development. Therefore it is nec¬ 
essary in flowing on the developer to have 
inst enough to cover the plate, as any of 
the solution allowed to spill over the edges 
will carry silver with it and thus prevent the 
image from becoming as dense as it might 
have otherwise. The acetic acid acts as a 
restrainer in that the silver, as fast as it 
is reduced, is made to discriminate between 
the various portions of the plate which have 
been acted upon most by light and those 
which have not. If no restrainer is used in 
the developer, a veil or fog will be seen to 
cover the plate, and the image will flash up 
as soon as the solution is poured over the 
surface. The correct time for development 
is between 20 and 30 seconds. A longer time y 
signifies under exposure, while a shorter time 
means that the plate has been over-timed. 
In development, the portions of the plate cor¬ 
responding to the white parts of the copy will 
be seen to get denser and denser, until a 


-15 



certain point is reached at which there is a 
pause. This is the signal to stop the action 
of the developer and the plate is immediately 
placed under the tap and washed thoroughly. 
And to wash well at this particular point 
is imperative, otherwise (in the subsequent 
operations a blue stain will appear. Over¬ 
development causes a fine deposit of silver 
to appear, in which should otherwise be the 
transparent parts of the negative, and under¬ 
development produces a thin image. 

FIXING 

At this stage of the process we have a 
film of unacted upon silver iodide and the 
negative image in metallic silver. This un¬ 
acted upon silver iodide must be removed 
from the plate so as to render it permanent 
and not susceptible to the further action of 
light. A solution strong enough to dissolve 
silver iodide and still not strong enough to 
dissolve metallic silver is what is desired. 
This is found in Potassium Cyanide and the 
result of the action of this substance is 
called “fixing”. Hypo-sulphite of soda may 
be used, but the cyanide works quicker and 
cleaner, and is more easily washed out of 
the film. The usual method of working is 
to mix a solution consisting of: 

Potassium or Sodium Cyanide 


(sat. sol.) .1 oz. 

Water . 5 oz. 


and flow over the plate until the silver iodide 
is thoroughly dissolved out of the film, which 
should take about twice as long as it takes 
the plate to clear. If there is a slight veil 
or scum over the surface of the plate which 
can be removed by rubbing with the ball of 
the finger, it is a sign of insufficient acid 
in the silver bath. 

INTENSIFYING 

The negative image is now in metallic 
silver alone, but before it can be used prac- 




tically, it must be intensified, so as to ob¬ 
tain an image in clear transparent lines cor¬ 
responding- to the black portions of the copy 
against a perfectly opaque background, thuo 
preventive any light from passing through 
during the operation of printing on sensi¬ 
tized metal. After thorough washing, we 
place the plate in a solution of: 

Potassium Bromide (sat. sol.)..l oz. 

Copper Sulphate (sat. sol.).8 oz. 

The Potassium Bromide and Copper Sul¬ 
phate combine to form Copper Bromide, 
which combines with the metallic silver in 
the imao-e to form silver bromide plus cop¬ 
per bromide. On placing the plate in the 
Copper Bromide solution, it will be seen to 
turn black and then slowly bleach out white. 
When the film has bleached clear through 
which is ascertained by looking at the glass 
side, the action has been carried far enough. 
In regard to washing the plate after taking 
it out of the Copper and before blackening 
in the silver intensifying solution—just enough 
water to wash the excess Copper and Bro¬ 
mide from the surface, for if too thorough 
a washing is given at this point, all of the 
Copper and Bromide will be washed out of 
the film and the plate will refuse to blacken 
in the silver. In fact, at no time should a 
strong stream of water be allowed to play 
on any one particular spot in the plate—it 
is much better to keep the plate moving 
while wash in e- Sometimes the plate when 
placed in the Copper will refuse to bleach 
out or at ahv rate very slowly. This is 
caused from an insufficient quantity of Po¬ 
tassium Bromide. However, too much Bro¬ 
mide will cause the plate to bleach TOO 
quickly and then it will not blacken well. 
N'ow then, after bleaching and washing, we 
are ready to intensify it in the silver inten¬ 
sifying bath. This is made up in exactly the 
same way as was the silver sensitizing so¬ 
lution, except that it should test about 25 



'decrees instead of 40 degrees. The longer 
the plate is left in this . solution, the denser 
it will become up to a certain point. Of 
course, the plate should at least be left in 
long enough to blacken through to the glass, 
which in all cases can be determined by look¬ 
ing at the glass side. In order to obtain per¬ 
fect density in the background, it is neces¬ 
sary to perform this operation of bleaching 
in the Copper Bromide and intensi^^" in 
the silver at least twice. If two times through 
is found insufficient, then continue the oper¬ 
ation until the desired results are obtained. 
If, however, after three or four Umes through, 
the image is still not dense enough, one will 
know that the negative was too thin tp start 
with. Exnerience, however, will teach one to 
know whether the preceding operations have 
been correct by the way the image comes up 
in the developer, so that further work on the 
plate can be avoided. Under-exposure is the 
most general cause of thin negatives, al¬ 
though, of course, there are many other rea¬ 
sons. A freshly made silver intensifying solu¬ 
tion will sometimes give streaks, but the ad¬ 
dition of a few drops of Nitric Acid will insure 
its working smoothly. The solution should 
be of the strength given, as the use of a 
weak bath is apt to give trouble in “cutting”. 
The plate may reduce suddenly and unevenly. 

“CUTTING” OR REDUCING THE IMAGE 

Now, after removing the plate from the 
silver for the final time, wash thoroughly and 
examine the transparent parts with a mag¬ 
nifying glass by holding the plate before the 
light. Tf they are seen to be absolutely clear, 
nothing further need be done, except to 
“blacken”, which will be explained later, but 
if there is seen to be a fine grain or deposit 
of silver, it must be removed or “cut out”, 
as it is called. This is done by applying a 
solution which will slowly dissolve the en¬ 
tire image. Naturally the thinnest portions 


- 


are affected first, and when the parts cor¬ 
responding to the black portions of the copy 
are seen to be perfectly clear, the action of 
the “cutting” solution is stopped. We take 
advant«o- e of the fact that silver iodide, of 
which the plate was originally composed, is 
soluble in cyanide. So we pour a solution of: 


Potassium Iodide .3 drams. 

Iodine (resublimed) .1 dram. 

Water . 6 oz. 


over the film until it has bleached to a yel¬ 
low, turning it to iodide of silver. This also 
intensifies the image greatly. The Potassium 
Iodide is necessary in order to dissolve the 
Iodine in the solution and also to aid in 
bleach’no' the negative. If too little Potas¬ 
sium Iodide is used, the bleaching action is 
slow, and if too much is used the negative 
bleaches out quickly end very little intensi¬ 
fication is gotten. After rendering the image 
soluble by applying the iodine, we proceed 
to flow over the plate a weak solution of ’ 
Potassium Cyanide—about V 2 dram to 8 or 
10 ounces of water. This slowly begins to 
dissolve away the image, and when the ac¬ 
tion has been carried far enough, as will be 
seen when the lines appear clear and trans¬ 
parent, the plate is washed thoroughly under 
the tap. 


BLACKENING 

To complete the negative, it is only nec¬ 
essary to blacken it. We do this by flow¬ 
ing over the plate a solution of: 

Sodium Sulphide (sat. sol.).1 oz. 

Water .6 to 10 oz. 

until it has blackened clear through. This 
changes the silver iodide of which the image 
was composed to silver sulphide—the black¬ 
est and most permanent state into which sil¬ 
ver can be changed. If a slight yellow stain 
should appear, it can sometimes be removed 
by flowing the plate over with: 






Nitric Acid .1 oz. 

Water . 20 oz. 


or, better still, an application of the Nitric 
Acid solution BEFORE blackening will gen¬ 
erally prevent the yellowness from appearing. 

OTHER METHODS OF INTENSIFICATION 

There are other methods of intensifying 
the image besides Copper and Silver, but this 
is the most universally used, as it is simpler 
to work md permits of- greater manipula¬ 
tion. However, for those who may be in¬ 
terested, we list the following: 

“LEAD” 

Where great intensification is desired, 


make up a solution of: 

Lead Nitrate .3 oz. 

Potassium Ferricyanide .3 oz. 

Glacial Acetic Acid (98 per cent) 3 oz. 
Water to make up to.64 oz. 


The plate is placed in this until bleached 
clear through to an even yellow, then washed 
thoroughly, flowed with the Nitric Acid so¬ 
lution (1 to 20), washed again and black¬ 
ened with Sodium Sulphide, after which it is 
again flowed with the Nitric Acid to prevent 
any possibility of staining. Any necessary 
reduction of the^ negative must be done im¬ 
mediately after fixing by flowing with Iodine 
and Cyanide, as it cannot be done after¬ 
wards. This intensifier works very energet¬ 
ically .and is used mostly for coarse line work 
One drawback to its use is found in the fact 
that Lead intensified negatives are some¬ 
times hard to strip. 

“MERCURY” 

Sometimes for fine line work and where 
maximum density is not necessary, the Mer¬ 
cury intensifier is used. 







Mercuric Chloride .5 oz. 

Ammonium Chloride .3 oz. 

Water to make up to.64 oz. 


Bleach in this solution, wash, and black¬ 
en with Sodium Sulphide as usual. Any re¬ 
ducing’ in this case should also be done be¬ 
fore intensification. 

DEFECTS IN NEGATIVES 

The best plan when a trouble arises that 
you are not sure as to exactly what it is 
would be to eliminate one by one each of the 
three general sources from which all troubles 
arise aside from the camera, lens, etc. First 
look to the developer, then to the collodion 
and finally to the silver bath. Although the' 
logic of this order may seem reversed to 
some, still on trial, it will be readily seen 
that it is easier to test developer and collo¬ 
dion first and silver bath last than to work 
the other way to. 

THIN NEGATIVES 

Under exposure. 

Under development. 

Weak silver bath. 

Insufficiently iodized silver bath. 

Excess of add in silver bath. 

Plate not left in bath long enough. 

Bath too cold. 

Collodion too old or too thin. 

Intensifying chemicals not right. 

UNEVEN DENSITY 

Uneven flowing of collodion. 

Uneven flowing of developer. 

Uneven lighting of copy. 

Uneven ‘‘cutting” with cyanide. 

STREAKS 

Silver bath too strong. 

Not rocking plate when flowing collodion, 
or collodion being too thick. 


- 21 — 





Scum on surface of bath. 

Plate being stopped when lowering 


in 


silver bath. 
Removing 
Alcohol in 


plate from bath too soon, 
bath causing developer to flow 


uneven. 


TRANSPARENT SPOTS 


Dust in collodion or silver bath. 
Overiodized silver bath. 
Undissolved salts in collodion. 


BLURRED OR DOUBLE IMAGES 

Improper focusing. 

Dirty lens. 

Movement of lens, plate, or copy-board 
during exposure. 

FOG 

Light struck. 

Insufficient acid in silver bath. 

Bath too warm. 

Insufficient acid in developer. 

Developer too strong or too warm. 

New or unripened collodion. 
Over-exposure or over-development. 
Fumes of chemicals, such as Sulphide, etc. 

OYSTERS 


Dirty plate, plate holder, blotters, wiping 
cotton, etc. 

Prolonged exposures, especially in hot 
weather. 

YELLOW STAINS 


Collodion not dried enough or too thick. 
Not washed enough between chemical 
operations. 

Old or too strong a sulphide solution. 


THE H^LF-TONE PROCESS. 

(Everton Method.) 


The fore part of this book dealt with the 
practical working methods of producing neg¬ 
atives to be used for the Line Photo-Engrav¬ 
ing process; that is, the reproduction of cop¬ 
ies in which there were only two tones— 
black and white. We shall next consider the 
methods and means by which photographs, 
wash drawings or any other copies which have 
gradations between black and white, can be 
reproduced by what is known as the half-tone 
process. 

To begin with, it is necessary for us to 
remember that the image in a photo-engraved 
plate is in relief and in the same plane, and 
that all parts are covered with a laver of 
ink OF THE SAME THICKNESS when a 
roller is passed over the plate. Therefore, 
to obtain the effect of tones other than black 
and white, it is necessary for us, not to vary 
the thickness of the ink (which is a physical 
impossibility in the typo-graphic printing 
process) but to have small areas in perfect 
proximity to one another and varying in size. 

THEORY 

This is accomplished by breaking up the 
continuous tones in the original photograph 
into dots of different sizes by. placing in front 
of the sensitive plate during exposure a 
screen or grating, the small transparent holes 
in which act as lenses to the light passing 
through. That is, each bundle or rays as it 
strikes the opening will be concentrated and 
brought to a point of focus on the sensitive 
plate. The theory underlying this screen ac¬ 
tion is based on the law of optics, which says 



that light after passing- through any open¬ 
ing, whether round, angular, or square, will 
conform itself into a round pencil of rays 
with the greatest intensity at the center, if 
given sufficient space. One can compare 
light on passing through some small opening 
under the conditions iust mentioned to sand 
passing through the small opening in an hour¬ 
glass. The sand as it piles up forms a nvr- 
amid or cone, and the longer the sand trickles 
through the opening, the larger the pyramid 
grows. This is exactly what haooens when 
light passes through one of the small open¬ 
ings in a half-tone screen. It forms a dot 
with the greatest density at the center and 
the ultimate size of which depends on the 
amount of light which has acted upon it. 


THE HALF-TONE SCREEN 

Just a word now. before continuing, as 
to the nature of the half-tone screen which 
we use. It is made as follows: Two nieces 
of optically plane glass are covered with an 
acid result. They are then placed in a spec¬ 
ially constructed machine, invented by Max 
Lew. at Philadelphia, Pa., and ruled in par¬ 
allel lines any number to the inch with a fine 
point which scratches through the resist coat¬ 
ing. leaving the glass clear. It is then flowed 
with hydrofluoric acid until the glass has 
etched slightly. All traces of the acid resist 
film are cleaned off and the indentations made 
hv the acid are filled with a black pigment. 
The two pieces of glass with their lines 
crossing each other at an angle of 90 degrees 
are cemented together with Canada balsam, 
and the edges bound together with alumi¬ 
num to protect them from injury. One of 
these pieces of glass is always made of the 
same thickness (3{32 in.) to facilitate accur¬ 
ate measurement of the distance between sen¬ 
sitive plate and screen ruling or screen sep¬ 
aration as it is known. This thin or cover 


- 24 - 


glass side of the screen is distinguished by 
the manufacturer's name, patent, date, etc., 
being engraved in the aluminum edging. 

In the sketch below, the terms, such as 
screen opening, screen ratio, etc., become 
readily apparent. The opaque lines in the 
screen are ruled at an angle of 45 degrees 
with the sides of the plate. This is because 
the dots or screen effect in the final repro¬ 
duction is less noticeable, as will be readily 
seen by just looking at a newspaper half¬ 
tone right side up and then without moving 
it nearer or closer, twisting it a quarter turn. 









FINDING SEPARATION AND STOPS 
TO USE 

The drawing is to represent the rays of 
light passing through the lens, through an open¬ 
ing in the screen and finally striking the piale. 
As mentioned before, it is necessary, in order 
that the light after passing through one of 



the openings in the screen can be concen¬ 
trated to a point on the sensitive plate, to 
have the distance between the opening and 
the sensitive plate correct, and this depends 
on the size of the opening in the screen. As 
will be seen from the illustration, hand in 
hand with this goes the size of the opening 
in the lens, as this alters the angle at which 
the light strikes the screen and plate. Vary¬ 
ing the stop or opening in the lens or the 
distance between screen and sensitive plate 
would give us like results. In order for us 
to fulfill the theoretical considerations here¬ 
tofore mentioned, it is necessary to estimate 
the variable parts of the equation accurately. 
It can be expressed in the following rule: 
Separation is to Screen Opening as Extension 
is to Stop. The practical working out of this 
problem in ratio is seen at the bottom of 
the table opposite. Another rule which works 
out the same as the one above is what is 





NORMAL SCREEN SEPARATION 
Basts on SH to tratio ; that Is 
Separation - 6 Xscreen opening 


50 = 

zo Zzz = 

5/3 

6 0 = 

/7 /3Z =. 

9 //e 

70 - 

'S/3Z = 

/ / 2 

80 = 
85 = 

/3 /az ? 

/2 -/3Z ) 

A/6 

90 = 
95 = 

V/ /32 l = 

"/3>Z J 

% 

/OO = 

no - 

/0 /3Z 7 

9 /3Z ) 

S //6 

/zo = 
/33 = 

9/32 ? 

8 /3 z) 

A 

/ 50 ■= 

7/3Z 


200 ^ 

5/az 


Z50 - 

'/■/a z - 

Vs 

300 = 

•3/32 


POO ~ 

z /az - 

V/6 

EXAMPLE 

Sep : S.O :: Lx.'. Stop 
/7 /3z '/,zo zv ^ 

— Z4 
/ZO ■ 

_ / • 17 
5 ■ 3Z 

= 3 J 

8 





















known as the 64 to 1 ratio; that is, Separa¬ 
tion is 64 times Screen Opening, and the Stop 
is 1(64 of the extension. The table gives the 
correct distance that the screen ruling should 
be placed away from the sensitive plate in 
32nds of an inch for all ordinary ruled screens. 

MAKING A TRIAL EXPOSURE 

Suppose now, after putting the desired 
screen in place in the plate-holder or cam¬ 
era and getting the correct separation by 
measuring, we focus a copy and prepare to 
make an exposure. Everything is handled 
the same as in line work until we come to 
exposing. Here we find it necessary to use 
a certain stop, the size of which is found 
according to the foregoing rules. The expo¬ 
sure is governed by the character of the copy. 
Upon examining the negative after develop¬ 
ing and fixing, we find that we have our image 
in dots of various sizes. In the parts cor¬ 
responding to the light portions of the copy, 
the dots will be larger and in the dark por¬ 
tions, smaller because for a given length of 
time more light is reflected from a white 
part of the copy than a dark. 

However, if we look in certain parts of 
the negatives wherein the copy, it was per¬ 
fectly black and no light reflected, we will 
notice that there is no dot formation at all, 
and in the parts corresponding to the white 
portions of the copy, the dots are just touch¬ 
ing at the corners. 

WHY A “FLASH” AND “HIGHLIGHT” IS 
GIVEN 

Now. in negatives used for Photo-En¬ 
graving, it is necessary that we have a solid 
dot, though very small, even in the deepest 
shadows, and in the highlights, the dots should 
be of such a size that they overlap, so that 
in between a group of four there will only 
be a small transparent opening. Therefore, 


ul addition to our main or detail exposure, 
we generally give two short auxiliary expo¬ 
sures, known as a “flash” and a “highlight”. 
The “flash” exposure is made by using a 
small stop about one-half the size of the 
straight and exposing to a white sheet of 
paper for a period of time depending on the 
density of the shadows in the copy—for nor¬ 
mal work approximately one-tenth of the de¬ 
tail exposure. The “highlight” exposure is 
made through a stop about two-thirds larger 
than the straight for a length of time about 
equal to the flash and. of course, to the copy 
itself. 

For the “highlight” different shaped stops 
may be used, the object being to make it 
easier for the dots to connect at the corners, 
this being possible because of the fact that 
the shape of the dots take the form of the 
stop used if sufficient exposure is given. The 
dotted lines in the drawing of the half-tone 



screen show the projected image of a square 
stop, and from this it can readily be seen 
why the dots will connect at the corners 
easier if a square, or a square with corners 
extended is used for the highlight rather than 
a round. 

RESULTS OF AN EARED STOP 

However, where we gain in ease of man¬ 
ipulation, we lose in the quality of our re¬ 
sults. When an eared stop is used for the 
highlight, the dots in the three quarter whites 
and middle tones have a tendency to connect 


- 20 — 



even for the shortest exposure and this, of 
course, means a loss of gradation in the light 
portions of the copy, as it will give broad 
areas of white without detail. This fact may 
be taken advantage of where great contrast 
is wanted, as then an eared or square stop 
is sometimes desirable. 

ROUND STOPS ARE BEST 

However, most operators of the present 
day will agree that when the best possible 
results are to be achieved in the use of ANY 
screen and a truthful reproduction of the 
copy gotten, round stops should be used for 
all exposures. To the beginner this may 
seem a trifle hard, as it is more difficult to 
obtain good connections in the highlights 
when a round stop is used, so for that rea¬ 
son I advocate the use of a square stop to 
start with, but to work with round stops ex¬ 
clusively should be the aim of all conscien¬ 
tious workers. 

METHODS OF WORKING 

Now, as to the methods of working. Af¬ 
ter we have put a new copy on the board 
and focused to the desired size, we have 
brought about a change—namely, the exten¬ 
sion. And this will call for a difference some¬ 
where if we are to adhere by our rules of 
proportion. In order to fulfill those require¬ 
ments, we must either change the separation 
or the size of stops. Most workers prefer 
to vary the lens aperature instead of the 
screen separation with every change of bel¬ 
lows extension, because there is more leeway 
m working considering the fact that to ob¬ 
tain good results, especially with a fine line 
screen, the separation must be correct al¬ 
most to the one-hundredth part of an inch. 
Then the only difference in handling various 
copies aside from the all important part of 
exposing is the size of the stops to use. 


— 30 — 


Table of normal s/se slops for use 
with different bellows extension on 
the basis of 'f/ash " being / '/z the 
(diameter of detail or straight" and 
the length of one side of square or eared 
highlight stop being z /i larger than ‘detail ' 

Extension 

F/ash ° 

Detail ° 

ttghliqhl'R 

8 

/ //6 

V 8 

7/sZ 

/z 

3 /sz 

3 /l& 

V/6 

16 

V8 

'if 

/3 /3Z 

2.0 

5 /3Z 

S//6 

'Vs z 

24- 

S//6 

3 /& 

4/8 

28 

7/3Z 

7/,S 

Z-'/az 

32 

'/* 

'/z 

Z-V3Z 

36 

g /3Z 

9//6 

r 

40 

V/6 

5/6 

//3 Z 

44 

/// 3Z 

"//6 

/ Vsz 

48 

3 /a 

3/4 

/ V4 

ifround stops are used for highlight Jet 

the diameter be equal to the diagonal 
of proposed square, stop 7 r 

' To 'find the equu/alent area of a go- 
uare giuen diameter of cirde'Multiply 
the diameter of circle by0.866which 
will give length of one side of square. 


31 






















Therefore, for the same copy, no matter what 
the enlargement or reduction, we would al¬ 
ways give the same exposures providing we 
used stops in accordance with out calcula¬ 
tions. For handy reference to be used as a 
basis frcm which to work, I have provided 
a table which gives the sizes of stops 10 use 
for different bellows extensions. 

NECESSITY OF CONVERTING F NUM¬ 
BERS INTO INCHES 

As the size of stops to use for the dif¬ 
ferent exposures is computed in inches, it is 
necessary for us to convert the F numbers 
on the lens if the lens is provided with an 
“iris” diaphragm into inches. The table fol¬ 
lowing gives the nearest equivalent readable 
fractions of an inch of the lens openings, for 
the different focal lengths of lenses used. To 
find the size in inches of F 8, for example, 
on a lens with a different focal length, simply 
divide the focal length by 8 and so on for 
the other F numbers. 

FINDING FOCAL LENGTH OF LENS 

If the focal length of the lens in use is 
not known, then focus a copy same size, 
measure the distance from ground glass to 
copy board and divide by four, which will 
give the correct focal length. 

In some cases of a great enlargement, 
it might so happen that according to calcu¬ 
lations, our highlight stop would be larger 
than the lens would allow, so we simply move 
the ruled screen farther away and then figure 
the size of stops according to the given rule. 

EXPOSING FOR DIFFERENT KINDS OF 
COPIES 

As to exposing for different kinds of 
copies. In the first place we must remem¬ 
ber that our object is to start with as small 
dots as possible, consistent with hardness, m 


Fnumbers and iheir equivalents 
for focal lengths of-- 

FOCAL 
LENGTH 
OF OASES 

9 

// 

/2 

/3 

/y 

/5 

F& 

F/o 

/7a 

F/z 

m 

/% 

/ 7 /q 

7/ 

TV 

/ 

/ 

i'/z 

/7y 

F/v 

r /6 



J /y 

yy 

//6 

/ 

*zz 

7s 

v? 

//£ 

TV 

7s 

J /y 

f 3Z 

/y 

TV 

J /<5 

y§ 

% 

TT 

'F 

% 

7/ 

TV 

7 /y 

77 

77 


V<3 

3 //6 

y<? 

TV 

TV 

TV 

FOCAL 
LENGTH 
OF OASES 

/ 6 

/7 

/'<3 

/9 

20 

2y 

"a 

2 

27a 

27y 

F/ d 

27 

a 

7/ 

/V 

/72 

F/z 

//V 

2 

2 

r /6 

/ 

/ 

/7s 


/7* 

F/z 

72 

->/y 

TV 

J /y 

/ 

/ 

/ 

72 

7> 

//z 

*/z 

ys 

7s 

J /y 

V5 

% 

ys 

ys 

vs 


72 

6y 

TV 

7y 

y*> 

TV | TV 

J /s 


— 33 — 



























the shadow portions, and from that grow 
gradually in size until they touch at the cor¬ 
ners and finally overlap. If the dots were 
all of the same size, we would have no im¬ 
age, as it is only in their variations that we 
obtain detail. That must be kept in mind 
when giving the different exposures. A cer¬ 
tain size stop will on exposure allow the dots 
to grow to a certain size and stop. Of 
course, there will still be a little spreading- 
action of the light beyond this, but not enough 
to affect the results materially. Now, sup¬ 
pose we are giving the straight exposure. 
If the dots in the lightest portions have 
grown as large as they will and we continue 
exposing, the dots representing the tones 
lower down will continue to grow, and if this 
is carried too far, we will have what is 
known as a high-key negative; that is, one 
in which the general tone of the picture is 
too light and a faithful reproduction of the 
original will not be gotten. On the other 
hand, if too short a straight exposure is 
given, we will have a low-key negative, and 
the general tone of the picture will be too 
dark. In other words, we desire to get as 
much variation in the sizes of the dots as 
possible—this means detail and gradation. 
The “flash” exposure should only be sufficient 
to give a small hard dot in the deepest shad¬ 
ows. The “highlight” exposure will vary 
with the character of the high lights in the 
different copies. Aside from this, some 
etchers desire the transparent openings larger 
or smaller than others. The operator should 
learn to make them any desired size and then 
individual tastes can be catered to. All cop¬ 
ies, I think, can be divided practically into 
five different classes. We will take them up 
separately and attempt to suggest methods 
of exposing for each. 

1. Flat and Sepia copies: That is, one in 
which the shadows are gray or brown, not 
black, and the highlights are gray or yel- 


— 34 — 


low, not white. A short “flash” should be 
given, as during the “straight” exposure the 
small starting dots will grow larger in size 
as even the deepest shadows reflect light in 
a copy like this. A normal “straight” should 
be given. Naturally, it will take a longer 
“highlight” than usual, as there is not as 
much light reflected from a gray or yellow 
portion as from a white. 

2. “Contrasty”, one in which the shad¬ 
ows are very black and the highlights white. 
A longer “flash” than usual, a normal 
straight, and a short “highlight”. 

3. A copy in which the middle tones of 
the picture are too dark and the object is 
to lighten them slightly. In this case a nor¬ 
mal flash, longer “straight” and normal 
highlight should be given. 

4. Then, for one that is too light, a nor¬ 
mal flash, short straight, and a highlight 
long pngiv e the desired connections 
should be given. 

5. For GROUPED copies, pick out the 
deepest shadows and the highest points of 
light. Expose for these accordingly, giving 
a normal “straight”. 

Of course, there are exceptions to all 
rules, and the operator must use his own 
judgment, but from the foregoing sugges¬ 
tions. the exposures for other copies will pre¬ 
sent themselves. Sometimes it is not nec¬ 
essary to give as many as three exposures 
as in the case of a copy with very gray shad¬ 
ows, when no “flash” will be needed, or in 
the case of a copy in which the middle tones 
are dark and the “highlights” very white, 
then no “highlight” is given, as the dots 
will connect up sufficiently during the long 
“detail” exposure. Also, it is not always pos¬ 
sible or desirable to keep the stops in the 
proportions listed, as, for example, in the 
case of a copy with very gray or yellow high¬ 
lights, when an extra large highlight stop 
will have to be used. It is generally better 


in exposing for a copy with gray highlights 
to give a short exposure through a larger 
stop than the other way round, as sometimes 
when the dark portions reflect light, weak 
connections are apt to be built up between 
the shadow dots. Matte surface copies re¬ 
quire less “flash” and more “highlight”, while 
flossy copies necessitate more “flash” and 
less “highlight”. 

GETTING CONTRAST OR FLATNESS AS 
DESIRED 

To produce contrast, one should give a 
normal “flash”, short “straight” and a long 
“highlight” For detail, give a normal 
“flash”, long “straight”, and a short high¬ 
light”. The shadows in all negatives with 
any screen should be' 5 as small as possible, 
though very hard and dense. The highlight 
Openings on coarse ' screen negatives to be 
printed and etched on zinc should be very 
small, but in the negatives for “copper”," the 
finer the screen, the more “open” the high¬ 
lights should be so as to allow for etching 
down, thus obtaining depth and good print¬ 
ing qualities. 

MANIPULATION AT THE SINK 

In manipulating the negatives at the 
sink, one will soon learn to know just how 
many times to “copper” and “silver” before 
flowing with the iodine solution and “cutting”. 
The highlights will continue to intensify to¬ 
gether after the shadows have stopped grow¬ 
ing in size or at least more so in proportion. 
This, and the fact that a strong “cutting” 
solution has a tendency to “cut” shadows 
more in proportion to “highlights” and vice 
versa, may be taken advantage of in the case 
of a faulty exposure. Also after “cutting” 
the “highlights” may be greatly intensified 
by an application of copper and silver. 

After all is said and done, experience is 
the best teacher providing it is logically in- 


— 36 - 


dulged in under the surveilance of one who 
can offer helpful suggestions and give sound 
advice. So, when it comes to a chance for 
learning grasp every opportunity, as today 
it is the man who knows and knows he knows 
and isn’t afraid to make good use of his 
knowledge that is in demand. 

RESULTS OF WRONG SCREEN SEPARA¬ 
TION AND SIZE OF STOPS 

If, on examining the negatives after 
“fixing”, we find that the shadow dots are 
square and the high lights “open”, providing 
the correct stops have been used and an ade¬ 
quate exposure given, it is a good sign that 
the screen is too close. On the other hand, 
if the shadow dots are very fuzzy and the 
highlights closed and fuzzy, then the sep¬ 
aration is too great. If the highlights or 
the shadows are affected separately, then we 
know that it is either the size of stops wo 
are using or the exposure. 

SCREEN RULINGS AND WHAT USED FOR 

60—Rotary newspaper presses, where 
work is to be sterotyped. 

85—Flat-bed presses, used for small 
newspapers. 

120—Medium grade book and pamphlet 
work. 

133—Magazine and catalogue work. 

150—Best grade of catalogue work. 

200—Used only on the best grade of 
paper. 

300-400—Used very rarely and then only 
on double coated paper for microscopic re¬ 
productions, etc. 


—37 — 


Proportional Increase and 
Decrease of Exposure Erne 


'/z 

'/3 

'/4 

'A 

Vb 

Vr 

V& 

75 

22 

ZO 

19 

18 

17 

IT 

17 

.30 

45 

40 

37 

36 

3 5 

34 

33 

.45 

107 

700 

56 

54 

52 

5/ 

50 

too 

130 

720 

1,15 

772 

710 

708 

707 

1:15 

752 

740 

733 

730 

727 

725 

724 

130 

215 

ZOO 

752 

748 

745 

743 

741 

145 

237 

220 

215 

20b 

202 

2oo 

758 

ZOO 

3 00 

240 

230 

225 

220 

217 

215 

£15 

322 

500 

249 

242 

237 

254 

232 

230 

345 

520 

307 

3.00 

255 

251 

249 

245 

407 

540 

3-26 

3:i8 

3.1 2 

308 

306 

300 

430 

400 

3.45 

336 

330 

326 

32Z 

315 

452 

420 

403 

554 

347 

343 

339 

£30 

5J5 

'440 

422 

44Z 

405 

400 

3:56 

535 

537 

457 

44/ 

430 

422 

417 

473 

400 

6P0 

5-20 

500 

448 

440 

434 

430 





























RECTIFYING AN OLD 
SILVER-BATH 


After long use, the -silver bath will be¬ 
come over-iodized, giving pin holes and also 
charged with ether and alcohol, this causing* 
the developer to flow greasy and uneven. 
When in this condition, the bath is practi¬ 
cally useless and should be given a complete 
rectification. Proceed as follows: First, neu¬ 
tralize with ammonia or bi-corbonate of soda. 
When neutral, the solution will neither turn 
blue litmus paper red, or red blue. A bath 
when acid will hold more organic matter in 
solution than when neutral or alkali—hence 
the reason for neutralizing it. 

Now pour the bath into approximately an 
equal amount of COLD water—never pour 
cold water into the bath. The sudden chil¬ 
ling throws the iodides out of solution, so 
that on subsequent filtering, the greater part 
of them are removed. Now boil the bath 
down until it is a pasty mass. At this po'nt 
brown fumes of iodine will be seen to rise 
in the form of vapor. After cooling, add 
water to the desired amount of bath and test 
for strength. After adding silver nitrate to 
bring it to 45 degrees, set in the sun until 
clear. When ready for use, filter into bath 
container and acidify. The important point 
to remember in conjunction with the silver 
bath is to keep it from being contaminated 
with foreign substances. Always keep all 
utensils separate that are to be used in the 
handling of the silver solution, and nine- 
tenths of the troubles frequently encountered 
will vanish. 



MISCELLANEOUS. 


HIGHLIGHT NEGATIVES are those in 
which the highlight portions are entirely 
closed or solid; that is, there are no trans¬ 
parent openings in between the dots. This 
effect can be gotten in most copies by just 
giving the usual exposures and then supple¬ 
menting these by a short auxiliary exposure, 
through regular high light stop, about one- 
half the length of time with the screen 
moved away from the plate as far as it will 
go. By sufficient intensification the highlight 
portions will close up altogether and be a 
solid mass. 

If this method will not give the desired 
results, then take the negative with the high¬ 
lights closed as much as possible, and from 
this make a contact positive. The highlights 
in the positive will then be represented by 
very fine pin point dots, which can easily be 
cut entirely away with the cyanide solution. 
Now, a negative made from this positive will 
have the highlights represented by solid 
masses just as is desired. 

BEN DAY EFFECTS over the white por¬ 
tions in line copies, such as dots of any size, 
parallel lines,’ or sausage shaped lines can 
be obtained direct in the negative. Set the 



screen at the correct distance, insert one 
of the stops suggested in the illustration 
and expose to a white sheet of paper for 
a sufficient length of time to obtain good 


- 40 - 



density. Now move the screen as far away 
as it will go or remove it altogether and 
make a normal exposure to the line copv it¬ 
self through the stop ordinarily used for this 
work. On development, the imao*e will be 
solid and the rest represented by dots or par¬ 
allel lines or bologna shaped lines, as the 
case may be. 

A tooled effect in the highlights when 
making a negative of an ordinary photograph 
can be gotten by using the slit or elliptical 
stop for the highlight exposure in place of 
the usual round or square. 

As to the sizes for the slit or elliptical 
stops, the width at the center should be equal 
to the diameter of correct straight stop and 
the length equal to the diagonal or diameter 
of proportional highlight stop. 

Many other effects can be gotten by mak¬ 
ing two negatives of an original copy—one 
in which the “flash” and “detail” have been 
given, and the other with only the “high¬ 
light” made through some special shaped stop 
—and then stripping one on top of the other. 

POSITIVES of either line or half-tone, 
negatives can be made in two ways. If a 
same size positive is wanted, it may be made 
by contact in the plate holder. Place the 
negative and sensitized plate emulsion to 
emulsion, with pieces of blotting paper at the 
corners to separate them from actual con¬ 
tact, on the clips in plate holder, and expose 
to a white sheet of paper for the same le"<*th 
of time and with the same stop as would be * 
used in making an ordinary line negative. 

If the positive is to be made larger or smaller 
than the original, then the negative must be 
placed in a “kit” in front of the lens and 
focused accordingly. The other operations 
used from exposing are the same as in the 
usual line work. 


- 41 — 


MEZZOGRAPH SCREEN NEGATIVES 

The Wheeler Mezzograph screen, although 
not used very extensively, can still be made 
good use of by those who are willing to see 
some of its points of superiority—namely, 
those in which a result is desired other than 
the mechanical effect of geometrically spaced 
dots produced by the half-tone screen. It is 
made by flowing an acid resist medium, sol¬ 
vent in alcohol, over an optically plain piece 
of glass. The alcohol evaporates, and as the 
Pyrobetulin dries, it reticulates, and the 
cracks thus formed are of an irregular na¬ 
ture. The plate is now etched slightly with 
hydrofluoric acid. The resist medium is re¬ 
moved and the screen is complete. Varying 
the thickness of the acid resist and chang¬ 
ing the amount of solvent used, will produce 
screens having varying degrees of texture, 
which may be compared with the regular 
half-tone screens in their uses. The methods 
of working is similar to the ruled screen, ex¬ 
cept that it must be placed much closer and 
a single stop and exposure will generally be 
found sufficient. F45 will be about right, 
and the exposure will depend on the amount 
of enlargement or reduction and the char¬ 
acter of the copy. If on examining the neg¬ 
ative after fixation, it is seen to consist prin¬ 
cipally of small round dots with fuzzed edges, 
then the screen is too far away, or if the 
negative seems to be sharp, but made up of 
little irregular blotches with curly tails pro- 
truding from them, then the screen is too 
close. Generally once or twice through cop¬ 
per and silver will be enough to produce a 
good printing negative, as hardly ever is the 
iodine and cutting solution necessary. 


SPLICED NEGATIVES 


Spliced negatives are those in which dif- 
ferent parts of the image are on separate 
plates. The mam points to remember for this 


- 42 — 


work are not to change the size of the co^v 
for the separate exposures and to have enough 
of the image on each plate to allow for over¬ 
lapping in the “stripping”. The other man¬ 
ipulation for either line or half-tone, are 
carried on in the usual manner for the sep¬ 
arate processes. 

THREE AND FOUR COLOR WORK 

This is an advanced branch of half-tone 
operating, but any good black and white 
operator will have little trouble in mastering 
its details, if he will but give it the neces¬ 
sary thought and study. The magnitude of 
this subject is so great that it hardly comes 
within the scope of this small book. The 
working details may be found in the booklets 
put out by the different dry-plate manufac¬ 
turers. 



- 43 - 


AVOIRDUPOIS WEIGHT — 

¥3 7 Vz Grains = / Ounce 
16 Ounces _ = / Pound 

APOTHECARIES WEIGHT 
ZO Grains - / Scruple 

3 Scruples or60 6rains - / Dram 
8 Drams or ¥60Grains = / Ounce 
/Z Oun ces f l_Po und 

The 7z Scruple weight = 10 Grains 
" Scruple " r 20 ' 

// Z " " = ¥0 » 

» Dram " = 60 " 

" Z " " - tzo - 

" c3 " " -/<50 " 


FLUID MEASURE 

60 Minims 

* /Fluid Drachm 

8 Drams 

* / Ounce 

/6 Ounces 

- /Pint 

8 Pints 

= / Gallon 


PRINTERS MEASURE 
72 Points - i Inch. 

IZ Points - I Pica-Em 
6 Pica Ems - / Inch, 
13 Pica Ems = /Column 


-44 - 










CHEMICALS USED IN OPERATING, AND 
THEIR SYNONYMS 


The terms, V. S. P. and B. P., refer re¬ 
spectively to the United States Pharmacopeia 
and British Pharmacopeia. The grade C. P. 
is usually the purest obtainable. The grade, 
“Technical”, is the ordinary commercial prod¬ 
uct, and may be crude, pure or “C. P." 

SODIUM HYDROXIDE (Caustic soda. 
Sodium hydrate) N.aO.H. 

Color and properties: White, deliques¬ 
cent pieces, lumps or sticks. Keep well stop¬ 
pered, absorbs water from the air. 

Containers: Iron drums. 

Fire hazard: Dangerous. 

Railroad shipping regulations: Yellow 
label. 

POTASSIUM CARBONATE (Potash, 
Pearlash, Salts of Tartar). 

Color and Properties: White deliquescent, 
granular powder; alkaline reaction. 

NITRIC ACID (Aqua fortis, Hydrogen 
nitrate) H.N.O.a 

Color and properties: Transparent, color¬ 
less or yellowish, fuming, suffocating, caustic 
and corrosive liquid. 

Grades: Technical (usually 36 degrees to 
44 degrees Re.^ Grade generally known as 
Aqua fortis, being about 4l 1 / £ degrees Re., or 
65.67 per cent H.N.Oo; V. S. P.; B. P.; 
Pure. 

Strength of solution: 38 degrees, 40 de¬ 
grees, 42 degrees, 43 degrees Re. 

Containers: Carboys; glass bottles. 

Fire hazard: Dangerous. 

Railroad shipping regulations: White 
label. 

ALBUMEN, EGG: Fresh white separated 
from the yolk, diluted with water, beaten 
to a froth and subsequently filtered and evap¬ 
orated. Alkaline reaction. 


— 45 — 


COLLODION (Pyroxyline; Flexible col- 

l°di°Derivation; Solution of nitrated cellulose 
in ether and alcohol. 

Color and properties: Pale yellow, sirupy 
liquid; very inflammable. 

Fire hazard: Dangerous. 

Railroad shipping regulations: Red labei. 

NITROCELLULOSE (Gun-cotton). 

Color and properties: Yellowish, amor¬ 
phous lumps; inflammable, explosive. 

SolubL In a mixture of alcohol and ether. 

InsoluMe in alcohol, water and ether. 

Derivation: Hanks of cotton, free from 
impurities, are nitrated in mixed acid, re¬ 
moved from the acid, whizzed in a centrifuge 
to remove as much acid as possible, washed 
in water until no acid reaction remains, and 
finally boiled in several changes of water. 

Containers: Wooden boxes. 

Fire hazard: Dangerous. 

Railroad shipping regulations: Prohibited 
by express. 

ETHYL ALCOHOL (Grain alcohol; Fer¬ 
mentation alcohol; Cologne spirit; Spirits of 
wine.) C.2H. 6 .O.H. 

Color and properties: Colorless, limped, 
volatile liquid; ethereal; pungent taste. 

Denatured alcohol is an alcohol rendered 
unfit for human consumption by the addition 
of menthyl alcohol. 

ETHER (Sulphuric ether; Ethyl ether; 
Ethyl oxide). 

Color and properties: Very light, trans¬ 
parent, colorless, volatile, exceedingly inflam¬ 
mable, mobile liquid, pleasant aromatic odor. 

Derivation: By the action of sulphuric 
acid on ethyl alcohol, followed by distillation. 

AMMONIUM IODIDE N.H.H.—White 

Crystals. Soluble in water and alcohol. 

CADMIUM IODIDE C.dl.«— Colorless, 
flakey crystals. 

Soluble in water, alcohol and ether. 


CALCIUM CHLORIDE C.2C.1.’ — wnite, 
deliquescent crystals, granules or lumps. 

STRONTIUM CHLORIDE S.rC.I. - 
White, crystalline needles; sharp, bitter taste. 

Soluble in water and alcohol. 

SILVER NITRATE (Lunar caustic) 

A.gN.0.3 

Color and properties: Colorless, crystal 
plates, darkening on exposure to light in pres¬ 
ence of organic matter, caustic metallic taste; 
poisonous and corrosive. 

Derivation: Silver is dissolved in dilute 
nitric acid, the solution evaporated. 

Imprints: Copper nitrate. 

Containers: Amber or black glass bottles. 

Fire hazard: Dangerous. 

Railroad shipping regulations: Yellow 
label. 

IRON SULPHATE (Ferrous sulphate; 
Copperas; Green Vitrol) F.eS.O.*-, 7H.‘0. 

Color and properties: Greenish crystals, 
often musty in color from oxidation and efflo¬ 
rescence. 

Soluble in water, insoluble in alcohol. 

Derivation: A‘by-product from the manu¬ 
facture of steel, and by the action of dilute 
sulphuric acid on iron and with subsequent 
crystallization. 

ACETIC ACID H.C. H ~0. 7 — Vinegar is 
a dilute, impure acetic acid. 

Strength of solution: 90 per cent, 80 per 
cent, 60 opr cent, 36 per cent, 30 per cent, 
2S per cent. 

Railroad shipping regulations: White 
label. 

POTASSIUM CYANIDE K. C. N. 

Color and properties: White amorphous, 
deliquescent lumps or crystalline mass; faint 
odor of bitter almonds; extremely poisonous, 
do not handle with bare hands! 

COPPER SULPHATE (Cupric sulphate; 
Blue vitriol; Blue stone) C.uS.O* 5HaO. 


47 


Color and properties: Blue crystals, slow¬ 
ly efflorescing in air; poisonous. 

Derivation: By the action of dilute sul¬ 
phuric acid on copper or copper oxid in large 
quantities, with evaporation and crystalliza¬ 
tion. 

POTASSIUM BROMIDE K. Br. 

Color and properties: White, crystalline, 
granules or powder; pungent, strong, bitter 
saline taste. 

IODINE I.* 

Color and properties: Purplish-black, flat, 
volatile crystals; poisonous, corrosive. 

Soluble in alcohol, chloroform, ether, 
glycerine and alkaline iodide solutions; insol¬ 
uble in water. 

Derivation: From the ashes of sea weeds 
or mother liquors of Chili saltpetre by the 
addition of sodium bi-sulphite solution. The 
precipitated iodine is collected and dried. 

POTASSIUM IODIDE K.i. 

Color and properties: White crystals, 
granules or powder; strong, bitter saline taste. 

Soluble in water, alcohol and ether. 

Grades: Crystals, granulated; powder; V. 
S. P.; B. P. 

SODIUM SULPHIDE (Sodium surphuret; 
Sodium monosulphide) N.a S. 

Color and properties: Yellowish or brick- 
red lumps; soluble in water. 

AMMONIUM CHLORIDE (Sal ammoni¬ 
um) N.H. 4 CI. 

Color and properties: White crystals; 
commercial actical grayish. 

CADMIUM BROMIDE C.dBr 2 

Color and properties: Yellowish, crystal¬ 
line powder. 

AMMONIUM HYDROXIDE (Aqua am¬ 
monia; Ammonium hydrate) N.H^O.H.; 
Colorless liquid. 

MERCURIC CHLORIDE (Corrosive sub- 


48 


limate; Mercury bi-chloride; Mercury chloride, 
corrosive.) H.gCJz 

Color and properties: White crystals; 
very poisonous! 

Grades: Technical; lump; crystals; gran¬ 
ular, powder; V. S. P.. B. P. 

LOAD NITRATE P.b (N.0 2 ) 3 

Color and properties; White crystals. 

Derivation: By the action of Nitric acid 
on lead. 

Fire hazard: Dangerous. 

Railroad shipping regulations: Yellow 
label. 

POTASSIUM FERRICYANIDE (Red 
prussiate of potash; Potassium prussiate, Red) 
K. 3 Fe(C.N.) 6 

Color and properties: Bright red, lustrous 
crystals or powder; poisonous. 

SODIUM CYANIDE N.aC.N. 

Color and properties: White, deliquescent, 
crystalline powder; exceedingly poisonous. 



49 



INDEX. 


Line Negative Making . 

Line copies . 

Focusing the Image . 

Meaning of “Focal Length” ... 

( entering the Image . 

Avoiding Reflections . 

Removing old Film from Glass 

Al'bumenizing . 

Collodion . . :. 

Coating the Plate . 

Silver Bath .*.. 

Exposing Line Copies . 

Developing . 

“Fixing” Bath ... 

“intensifying” . 

“Cutting” or “Reducing” . 

“Blackening” . 

“Lead” Intensifying . 

Mercury Intensifying . 

Defects in Negatives . 


3-23 
. . .4 
. . .4 
.. .5 
.. .5 
. . .5 


.6 

.7 

.8 

10 

12 

14 

16 

16 

18 

19 

20 
20 
21 


The Half-Tone Process .22-34 

Theory .23 

Half -Tone Screen .24 

Finding Separation and Stops to use. .26 

Making a Trial Exposure .28 

Why a “Flash” and “Highlight” 

is given .28 

Results of an Eared Stop.29 

Round Stops .30 

Methods of Working .30 

Converting F Numbers to Inches.32 

Finding Focal Length of Lens.32 

— 50 — 

































Exposing for Different Kinds of Copies 32 

Getting Contrast or Flatness .36 

Manipulation at the Sink .36 

Results of Wrong Screen Separation 

and Size of Stops .37 

Screen Rulings and What Used for....37 

Rectifying an Old Silver Bath .39 

Miscellaneous .40 

Highlight Negatives .40 

Ben Day Effects .40 

Positives . 41 

Mezzograph Screen ...42 

Spliced Negatives . 42 

Three and Four Color Work?.43 

Tables of Weights and Measures.44 

Chemicals Used and Their Synonyms.45 

































































































\ 
























































































































































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